A huge white cloud envelops the cockpit of the Chinook helicopter as it settles into a hover ready for landing, blowing snowflakes from the ground into the air around the aircraft.

The view outside is suddenly and completely obscured, making it impossible to judge how close the vibrating machine is to the earth’s surface.

We’re effectively blind and as I lack the necessary skills and experience to put the Chinook down safely, an experienced ex-military instructor takes the controls.

A sense of relief washes over me as the helicopter touches down gently before my seat again begins vibrating as the engines strain to lift the multi-million pound machine back into the air.

Big beast: The RAF Benson site runs simulators for Chinook (pictured), Puma and Merlin helicopters used by Britain’s armed forces

It’s an ultra-realistic introduction to the hazards of flying military helicopters. But despite the shock-load to my nervous system, we’re actually sitting inside a white box in Oxfordshire – albeit a very expensive one.

RAF Benson is the home of aviation specialist CAE’s medium support helicopter aircrew training facility, a world leader in flight training for military and civilian pilots and aircrews.

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A joint venture between Canada’s CAE, which owns 76 percent, and quoted PFI specialist HICL, the Benson site runs simulators for Chinook, Puma and Merlin helicopters used by Britain’s armed forces.

But it’s a testament to the quality of the kit that flyers from allied nations as far afield as Australia and Canada travel thousands of miles to be put through their paces with synthetic training.

Following an initial capital investment of £100million, the facility is set up as a 40-year private finance initiative contract running until 2037 – it is due for a mid-life review in 2017 – with the Ministry of Defence paying by the hour.

FACT BOX: Medium Support Helicopter Aircrew Training Facility

40 years – duration of the PFI, with review due in 2017

£100million – initial investment with more spent since

10 per cent – approximate cost compared with real-world training

9,000 hours – flown annually, plus around 2,000 sold to outside users

£1billion – estimated annual cost-saving to the Ministry of Defence

6 – number of CAE simulators based at RAF Benson, Oxon

One of the first MoD PFI projects when it was signed in 1997, the so-called synthetic training facility was delivered on time and, according to a 2008 National Audit Office report: ‘the structure of the contract is working well’.

This is in sharp contrast to some PFI deals which have been slammed for being late and over-budget.

Today some 9,000 hours are ‘flown’ each year in the high-tech simulators, the equivalent to flying around 26 real helicopters and representing a £1billion saving to the taxpayer, according to CAE.

After the NAO report noted an unexpectedly low take-up in the early years, CAE’s Andrew Naismith says usage has been steadily increasing in the past five years.

Independent defence analyst Howard Wheeldon says: ‘Using the PFI process in the synthetic training model has already brought extensive benefits, not just to the MoD in terms of cost and extension of what can now be offered and achieved in terms of the training. But it is one that is now also benefiting our NATO allies and defence export customers.’

Soft landing: Before deploying to Afghanistan, many RAF and Royal Navy pilots use the simulators at RAF Benson to practise landing in desert conditions

Using simulators is attractive to the military. Not only are they safer, environmentally friendly and cheaper – around 10 per cent of the cost per flying hour of using real aircraft, which for a Chinook is about £20,000 – they enable flyers to rehearse difficult missions or challenging conditions.

Before deploying to Afghanistan, many RAF and Royal Navy pilots would use the simulators to practise landing in desert conditions, where billowing sand clouds have the same effect on landings as our simulated snow storm.

Naismith, a former Chinook pilot and RAF squadron commander, says: ‘The environment is so immersive that you do not realise that you are not flying the real aircraft.’

Student pilots are also introduced to their new helicopters in the 15 tonne simulator to familiarise themselves with various on-board equipment such as radios and also train for emergencies like engine failure in flight. In this way they save valuable time which would have been spent flying in a real aircraft.

Observing all this activity from their perch in the Tactical Control Centre, a room packed with TV screens and complex computer equipment, skilled instructors and technicians monitor students and experienced aircrews flying the simulators.

They can throw various scenarios at the flyers to help their training. The control centre is also capable of linking up the simulators so that pilots fly in realistic missions, including a ‘Thursday War’ where aircrews participate in a big combined military exercise.

Syd Exton, chief instructor, says: ‘The impression for the crews is ultra-realism. They forget they are in a white box in Oxfordshire. When they step out of the simulator after three hours they are better than when they went in there.’

So successful has been the military’s adoption of flight simulation that there is an aspiration to make it more than 50 per cent of training regimes.

According to Wheeldon, while hard-pressed defence budgets are the main reason for this shift, the level of realism afford by modern synthetics means the complete mission training it enables is increasingly important.